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If you have Aggressive Email Banning set to yes then, for example, entering e.e in Banned Email Addresses would ban any email address where e.e appears; otherwise with Aggressive Email Banning set to no, only email addresses ending in e.e would be banned. The same goes for .com or .edu assuming you are using a version of vB where Aggressive Email Banning is available. If interested, the is_banned_email function in the functions_user.php file shows how email addresses are marked for bans.